SHE appeared to have it all and do it all: a stellar career on civvy street that saw her work for the Prime Minister and a military prowess that made her a high-flyer in the Army Reserve.

Vicky was headhunted by drinks giant Diago after 21 years in Whitehall [IG]

In fact, so keen were Army top brass to use her as an example of balancing high-profile civilian and Reservist jobs that she became a poster girl for the Ministry of Defence’s new campaign.

Yet Lt Col Vickie Sheriff’s Army role hit a sudden snag last month when she was headhunted from her post in the Department of Trade and Industry by drinks giant Diageo after 21 years in Whitehall.

Her lucrative appointment as global director of communications meant something had to go, and she quit her senior Army role as head of a specialist media operations just months after taking it on.

Explaining her decision to step down from the Media Operations Group position, she admitted: “To try to juggle both jobs would be nigh impossible.”

It was only five weeks ago that the media star posed with David Cameron on Uniform to Work Day, part of a campaign to support Reservists.

Always ambitious, Ms Sheriff had joined the Army Reserve (formerly Territorial Army) as a Royal Signals officer but transferred to the Inns of Court Yeomanry, traditionally packed with City high flyers.

After staff college she was catapulted through the ranks, quickly becoming a major before being promoted to lieutenant colonel.

To try to juggle both jobs would be nigh impossible

Lt Col Vickie Sheriff

Senior officers at the Army Reserve Directorate stated Lt Col Sheriff was the “perfect example” of how people with high-powered civilian jobs could still join the Army Reserve and rise to the top.

So glowing were her reports that senior officers signed off her progress reports indicating she was “suitable for promotion to one star” – the shorthand for brigadier. At functions her connections to Downing Street ensured she was selected to escort senior officers, members of the Royal Family and other dignitaries.

Ms Sheriff’s triumphs in the Reserve mirrored her success in civilian life, which saw her become David Cameron’s deputy spokeswoman before being promoted to head of communications at the Department of Trade and Industry.

She had previously worked as Gordon Brown’s spokeswoman.

However, last month, in a letter to Colonel ‘PJ’ Lewis , her immediate commander, she said she was sorry but unable to give her full commitment to the command post and wanted to step back and find a less demanding reservist job.

In an internal document seen by the Sunday Express, she added: “I am sorry to be stepping down from this really amazing unit.

“But, as you know, I have been offered a very exciting job opportunity as the global director of communications for Diageo plc. To try to juggle both jobs would be nigh impossible.”

Her decision to quit her top Reservist role is a bitter disappointment to Army mandarins.

However, Col Richard Kemp, a former commander of British troops in Afghanistan, explained: “Reservists are people who choose not to make the Army their career, and therefore their commitment is not the same as a regular.”

Last night Ms Sheriff told the Sunday Express: “I continue to be in the Reserve, and it is important to say that my new employers, Diageo, are fully supportive.”